Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates to a push-button switch and, in particular, to an overload-protection push-button switch with a simple structure capable of actually tripping and automatically going to a reset position in case of overload, in which the moving direction of a push-button is vertical to the moving direction of a conducting leaf.
2. Description of the Related Art
There are many types of push-button switches for various applications, such as one having a turn-on indicating lamp and one providing an overload protection function. In terms of one having an overload protection function, there are also several kinds of protection principles or mechanisms being adopted. For example, both the blow-out of a fuse wire and the thermal deformation of a bimetal blade have ever been adopted as a trigger source for an overload protection. However, the fuse wire is not repetitive and thus its utility rate gradually decreases. As for the thermal bimetal blade, there are many kinds of mechanism, such as those disclosed in U.S. Pat. Nos. 5,786,742, 5,223,813, 4,937,548, 4,661,667, 4,931,762, 5,451,729, and 4,704,594.
For example, in the U.S. Patent No. 5,786,742, a so-called power-cutting member (72) used to alternatively set a set and a reset position of a switch is disclosed. In that case, a bimetallic blade (75) is used to push a shaft seat (71) to trip and automatically reset a switch. However, the contacts in such a switch are directly depressed by a button. Thus, if the button has jammed or pushed down by an external force, they would be kept in its conducting position even if overload occurs. Moreover, such a switch is not economical because of a use of up to four contacts to construct a conducting circuit. It also increases the possibility of generating an arc. Furthermore, it is troublesome in assembly due to a need for connecting a wire between the bimetallic blade (75) and the conducting plate (74).
In U.S. Pat. No. 5,223,813, a bimetallic blade (13), a common trip (17) actuated by the bimetallic blade and a cam member (27) are incorporated with a rocker actuator (33) to make contact members (7,1) contact to or separate from each other. In such a patent, the common trip (17) will be displaced in response to a deformation of the bimetallic blade so that the cam member (27) is released and the switch trips. However, even though the common trip is indirectly actuated by a rocker actuator so that a jamming of the rocker actuator or a contact of the contact members by a neglectful re-push after overload can be avoided, such a switch is rather complicated. Moreover, since it needs a wire to connect its cantilever spring (5) and its bimetallic blade (13), its assembly is also troublesome. Furthermore, a fail-action is possible in case of overload since the bimetallic blade may be unable to simultaneously actuate both of the rocker actuator (33) and the common trip (17).
In a circuit breaker disclosed in U.S. Pat. No. 4,937,548, a thermal actuator (76) is used to displace a lock lever (62) upon deformation so as to release a bell crank lever operator (52). In this case, even a jamming of the actuator and a connection between the contacts upon a neglectful re-push on the switch after overload can be avoided, such an arrangement has not an automatic resetting function and is difficult to install an indicator therein, Moreover, since two thermal actuators are forced against one biasing spring, a tilt of the two thermal actuators may happen.
In U.S. Pat. No. 4,661,667, a double-heart-shaped cam locking mechanism is used to obtain two locking-positions. However, such a switch has not an overload protection function and a status-indicating function.
A main object of the present invention is to provide an overload-protection push-button switch with an automatic resetting mechanism of pull-push type, which has a simple structure and a low manufacturing cost and is easy to assemble.
Another object of this invention is to provide an overload-protection push-button switch with an automatic resetting mechanism of pull-push type, in which the moving direction of the bush button is vertical to the moving direction of the conducting leaf and a trip function can be exactly performed in case of overload.
To achieve the above objects of this invention, this invention provides an overload-protection push-button switch with an automatic resetting mechanism of pull-push type comprising:
a housing;
a switching circuit installed in the housing, the switching circuit including: a first terminal, a second terminal, a first conducting leaf and a bimetallic blade, the bimetallic blade having a movable closed end which is able to move from a normal position to an overload position, and an open end formed with a first and a second legs which connect the first terminal and the first conducting leaf, respectively; the first conducting leaf being movable between a conduction position at which the second leg of the bimetallic blade is electrically connected to the second terminal and a broken position at which the second leg is disconnected from the, second terminal; and
an actuating unit installed in the housing, the actuating unit including:
a pressing stem received in the housing adapted to slide between a set and a reset positions;
a pull-push rod having two ends;
an enabling supporter being alternatively located in a supporting position and a tripping position in response to an allocation of the is bimetallic blade in its normal position and its overload position, respectively;
a floating rocker being formed with a nose for abutting against the first conducting leaf, a toe portion to be supported by the enabling supporter, a rod-engaging hole located between the nose and the toe portion to receive one end of the pull-push rod, a guided member for guiding a floating range produced by the rocker which is restricted by the pull-push rod, and a heart-shaped stepping recess located where the toe portion is;
a guider provided on the housing to match the guided member so as to limit the floating range of the rocker;
a cantilever having a fixed end fixed onto the pressing stem and a free end adapted to slide in the heart-shaped stepping recess;
whereby the toe portion of the rocker is enabled and disabled in response to the allocation of the enabling supporter in a supporting and a tripping position respectively in which when the toe portion is enabled the nose, presses and releases the conducting leaf to its conduction position and a broken position respectively in response to the allocation of the pressing stem in a set position and a reset position respectively under being driven by the pull-push rod and being limited by the guider; and when the toe portion is disabled the nose, the nose releases the conducting leaf to its broken position; and
the heart-shaped stepping recess departs from the free end of the cantilever when the toe portion is disabled so as to release the pressing stem to return to its reset position; and subsequently the toe portion of the rocker is pulled to a standby position so as to be supported and enabled by the enabling supporter again when the bimetaic blade returns to its normal position.
By means of the above structure, since the conducting leaf is indirectly actuated by the push-button via the pull-push rod and the floating rocker, the switch will exactly and transiently trip at the time overload occurs even if the stem jams. Moreover, by means of the cooperation of the pull-push rod, the guided member and the guider, the direction to press the push-button can be changed to being vertical to the moving direction of the conducting leaf so as to meet some special applications. By means of the integration of the heart-shaped stepping recess with the toe portion in the floating rocker, the pressing stem will be unlocked from its set position by means of the rotating of the floating rocker and automatically return to its reset position when overload happens. In the meanwhile, the toe portion can also return to a standby position under the action of the pull-push rod so as to be supported and enabled by the enabling supporter.